Method and apparatus for sensing an input object relative to a sensing region of an ultrasound sensor device

ABSTRACT

A subsystem, system and method for sensing an input object relative to a sensing region of an ultrasound sensor device are disclosed herein. In one embodiment, a subsystem for sensing an input object relative to a sensing region of an ultrasound sensor device includes a circuit, a switch coupled to an output of the circuit, and an integrating capacitor coupled to the output of the circuit. The circuit has an input for receiving a resulting signal comprising positive and negative polarities, the resulting signal having effects indicative of the input object relative to the sensing region. The integrating capacitor is also coupled to a substantially constant voltage source and to the switch. The circuit is operable to output a rectified signal to the first integrating capacitor indicative of the input object relative to a sensing region.

CROSS REFERENCE TO RELATED APPLICATIONS

This invention is a continuation application of U.S. patent applicationSer. No. 13/289,732, filed Nov. 4, 2011, which is incorporated byreference in its entirety, and which claims benefit of U.S. ProvisionalPatent Application Ser. No. 61/410,774, filed Nov. 5, 2010, and titled“TFT RECEIVER FOR PIEZOELECTRIC TRANSDUCER ARRAY”, which areincorporated by reference in their entireties.

FIELD OF INVENTION

Embodiments of the invention generally relate to a subsystem, a systemand method for sensing an input object relative to a sensing region ofan ultrasound sensor device.

BACKGROUND

Input devices including proximity sensor devices (also commonly calledtouchpads or touch sensor devices) are widely used in a variety ofelectronic systems. A proximity sensor device typically includes asensing region, often demarked by a surface, in which the proximitysensor device determines the presence, location and/or motion of one ormore input objects. Proximity sensor devices may be used to provideinterfaces for the electronic system. For example, proximity sensordevices are often used as input devices for larger computing systems(such as opaque touchpads integrated in, or peripheral to, notebook ordesktop computers). Proximity sensor devices are also often used insmaller computer systems (such as touch screens integrated in cellularphones).

Many commercially available proximity sensor devices utilized capacitiveand optical sensing. Capacitive sensing, although having a robusthistory of use, is susceptible to geometric distortion or edge effectsat the perimeter of the sensing region, and is also susceptible todamage and/or inaccurate output due to electromagnetic interference(EMI) and electromagnetic discharge (ESD). Moreover, capacitive sensingis limited to the detection of conductive objects relative to thesensor, thus limiting the types of inputs devices which may be utilized.The accuracy of optical sensing devices may be diminished due to theeffects of dirt, oils and other contaminants.

Ultrasound sensing has been recognized as a potential improvement fornext generation touch panel devices. However, significant challengesremain in the development of ultrasound sensing prior to acceptance forcommercially viable use.

Therefore, there is a need for an improved subsystem, system and methodfor sensing an input object relative to a sensing region of anultrasound sensor device.

SUMMARY OF INVENTION

A subsystem, system and method for sensing an input object relative to asensing region of an ultrasound sensor device are disclosed herein. Inone embodiment, a subsystem for sensing an input object relative to asensing region of an ultrasound sensor device includes a circuit, aswitch coupled to an output of the circuit, and an integrating capacitorcoupled to the output of the circuit. The circuit has an input forreceiving a resulting signal comprising positive and negativepolarities, the resulting signal having effects indicative of the inputobject relative to the sensing region. The integrating capacitor is alsocoupled to a substantially constant voltage source and to the switch.The circuit is operable to output a rectified signal to the firstintegrating capacitor indicative of the input object relative to asensing region.

In another embodiment, a system for sensing an input object relative toa sensing region of an ultrasound sensor device includes a detectionmodule having an input coupled to an array of sensor electrodes disposedon a substrate. The array of sensor electrodes are operable to provideresulting signals, each comprising positive and negative polarities inresponse to presence of the input object in the sensing region. Thedetection module is operable to integrate charges onto integratingcapacitors of the detection module with rectified signals in response toreceiving the resulting signals from the array of sensor electrodes.

In another embodiment, a method for sensing an input object relative toa sensing region of an ultrasound sensor device is provided thatincludes receiving a resulting signal and charging an integratingcapacitor with a rectified signal in response to receiving the resultingsignal. The resulting signal includes positive and negative polarities.The first resulting signal also includes effects indicative of the inputobject relative to the sensing region.

BRIEF DESCRIPTION OF DRAWINGS

So that the manner in which the above recited features can be understoodin detail, a more particular description, briefly summarized above, maybe had by reference to embodiments, some of which are illustrated in theappended drawings. It is to be noted, however, that the appendeddrawings illustrate only embodiments of the invention and are thereforenot to be considered limiting of its scope, for the invention may admitto other equally effective embodiments.

FIG. 1 is a schematic block diagram of an exemplary input device, inaccordance with embodiments of the invention.

FIG. 2 is a partial schematic of an exemplary input device illustratingan example of a ultrasound wave (i.e. a transmitter signal) interfacingwith an input object and a sensor module of the input object.

FIG. 3 illustrates an example stack-up of one embodiment of a sensormodule that may be used in the input device to sense the input object.

FIG. 4 is a partial cross sectional schematic view of one embodiment ofthe sensor element.

FIG. 5 is a schematic diagram illustrating one example of an array ofsensor elements configured as piezoelectric detectors coupled to adetection module of a processing system.

FIG. 6 illustrates one embodiment of a receiver circuit of a detectionmodule coupled to an output of a sensor module.

FIG. 7 is a flow diagram of one embodiment of a method for sensing aninput object relative to a sensing region of an ultrasound sensordevice.

To facilitate understanding, identical reference numerals have beenused, where possible, to designate identical elements that are common tothe figures. It is contemplated that elements disclosed in oneembodiment may be beneficially utilized on other embodiments withoutspecific recitation.

DESCRIPTION OF EMBODIMENTS

The following Description of Embodiments is merely provided by way ofexample and not of limitation. Furthermore, there is no intention to bebound by any expressed or implied theory presented in the precedingtechnical field, background, brief summary or the following detaileddescription. Various embodiments of the present invention provide inputdevices and methods that facilitate improved usability of a touch screendevice.

FIG. 1 is a schematic block diagram of an exemplary input device 100, inaccordance with embodiments of the invention. The input device 100 maybe configured to provide input to an electronic system (not shown). Asused in this document, the term “electronic system” (or “electronicdevice”) broadly refers to any system capable of electronicallyprocessing information. Some non-limiting examples of electronic systemsinclude personal computers of all sizes and shapes, such a desktopcomputers, laptop computers, notebook computers, tablets, web browsers,e-book readers, and personal digital assistants (PDAs). Additionalexample electronic systems include composite input devices, such asphysical keyboards that include input device 100 and separate joysticksor key switches. Further example electronic systems include peripheralssuch as data input devices (including remote controls and mice), anddata output devices (including display screens and printers). Otherexamples include remote terminals, kiosks, and video game machines(e.g., video game consoles, portable gaming devices, and the like).Other examples include communication devices (including cellular phones,such as smart phones), and media devices (including recorders, editors,and players such as televisions, set-top boxes, music players, digitalphoto frames, and digital cameras). Additionally, the electronic systemcould be a host or a slave to the input device.

The input device 100 can be implemented as a physical part of theelectronic system, or can be physically separate from the electronicsystem. As appropriate, the input device 100 may communicate with partsof the electronic system using any one or more of the following: buses,networks, and other wired or wireless interconnections. Examples includeI²C, SPI, PS/2, Universal Serial Bus (USB), Bluetooth, RF, and IRDA.

In FIG. 1, the input device 100 is shown as a proximity sensor device(also often referred to as a “touchpad” or a “touch sensor device”)configured to sense input provided by one or more input objects 140 in asensing region 120. Example input objects include fingers and styli, asshown in FIG. 1.

Sensing region 120 encompasses any space above, around, in and/or nearthe input device 100 in which the input device 100 is able to detectuser input (e.g., user input provided by one or more input objects 140).The sizes, shapes, and locations of particular sensing regions may varywidely from embodiment to embodiment. In some embodiments, the sensingregion 120 extends from a surface of the input device 100 in one or moredirections into space until signal-to-noise ratios prevent sufficientlyaccurate object detection. The distance to which this sensing region 120extends in a particular direction, in various embodiments, may be onethe order of less than a millimeter, millimeters, centimeters, or more,and may vary significantly with the type of sensing technology used andthe accuracy desired. Thus, some embodiments sense input that comprisesno contact with any surfaces of the input device 100, contact with aninput surface (e.g., a touch surface) of the input device 100, contactwith an input surface of the input device 100 coupled with some amountof applied force or pressure, and/or a combination thereof. In variousembodiments, input surfaces may be provided by surfaces of casingswithin which the sensor electrodes reside, by face sheets applied overthe sensor electrodes or any casings, etc. In some embodiments, thesensing region 120 has a rectangular shape when projected onto an inputsurface of the input device 100.

The input device 100 may utilize any combination of sensor componentsand sensing technologies to detect user input in the sensing region 120.The input device 100 comprises one or more sensing elements fordetecting user input. As several non-limiting examples, the input device100 may use ultrasonic, capacitive, elastive, resistive, inductive,surface acoustic wave, and/or optical techniques to provide one or moreresulting signals which include positive and negative polarities, theone or more resulting signals including effects indicative of the inputobject relative to the sensing region.

Some implementations are configured to provide images that span one,two, three or higher dimensional spaces. Some implementations areconfigured to provide projections of input along particular axes orplanes.

In FIG. 1, the processing system (or “processor”) 110 is shown as a partor subsystem of the input device 100. The processing system 110 isconfigured to operate the hardware of the input device 100 to detectinput in the sensing region 120. The processing system 110 comprisesparts of or all of one or more integrated circuits (ICs) and/or othercircuitry components; in some embodiments, the processing system 110also comprises electronically-readable instructions, such as firmwarecode, software code, and/or the like. In some embodiments, componentscomposing the processing system 110 are located together, such as nearsensing element(s) of the input device 100. In other embodiments,components of processing system 110 are physically separate with one ormore components close to sensing element(s) of input device 100, and oneor more components elsewhere. For example, the input device 100 may be aperipheral coupled to a desktop computer, and the processing system 110may comprise software configured to run on a central processing unit ofthe desktop computer and one or more ICs (perhaps with associatedfirmware) separate from the central processing unit. As another example,the input device 100 may be physically integrated in a phone, and theprocessing system 110 may comprise circuits and firmware that are partof a main processor of the phone. In some embodiments, the processingsystem 110 is dedicated to implementing the input device 100. In otherembodiments, the processing system 110 also performs other functions,such as operating display screens, driving haptic actuators, etc.

The processing system 110 may be implemented as a set of modules thathandle different functions of the processing system 110. Each module maycomprise circuitry that is a part of the processing system 110,firmware, software, or a combination thereof. In various embodiments,different combinations of modules may be used. Example modules includehardware operation modules for operating hardware such as sensorelectrodes and display screens, data processing modules for processingdata such as sensor signals and positional information, and reportingmodules for reporting information. Further example modules includesensor operation modules configured to operate sensing element(s) todetect input, identification modules configured to identify gesturessuch as mode changing gestures, and mode changing modules for changingoperation modes.

In some embodiments, the processing system 110 responds to user input(or lack of user input) in the sensing region 120 directly by causingone or more actions. Example actions include changing operation modes,as well as GUI actions such as cursor movement, selection, menunavigation, and other functions. In some embodiments, the processingsystem 110 provides information about the input (or lack of input) tosome part of the electronic system (e.g., to a central processing systemof the electronic system that is separate from the processing system110, if such a separate central processing system exists). In someembodiments, some part of the electronic system processes informationreceived from the processing system 110 to act on user input, such as tofacilitate a full range of actions, including mode changing actions andGUI actions.

For example, in some embodiments, the processing system 110 operates thesensing element(s) of the input device 100 to produce electrical signalsindicative of input (or lack of input) in the sensing region 120. Theprocessing system 110 may perform any appropriate amount of processingon the electrical signals in producing the information provided to theelectronic system. For example, the processing system 110 may digitizeanalog electrical signals obtained from the sensor electrodes. Asanother example, the processing system 110 may perform filtering orother signal conditioning. As yet another example, the processing system110 may subtract or otherwise account for a baseline, such that theinformation reflects a difference between the electrical signals and thebaseline. As yet further examples, the processing system 110 maydetermine positional information, recognize inputs as commands,recognize handwriting, and the like.

“Positional information” as used herein broadly encompasses absoluteposition, relative position, velocity, acceleration, and other types ofspatial information. Exemplary “zero-dimensional” positional informationincludes near/far or contact/no contact information. Exemplary“one-dimensional” positional information includes positions along anaxis. Exemplary “two-dimensional” positional information includesmotions in a plane. Exemplary “three-dimensional” positional informationincludes instantaneous or average velocities in space. Further examplesinclude other representations of spatial information. Historical dataregarding one or more of positional information may also be determinedand/or stored, including, for example, historical data that tracksposition, motion, or instantaneous velocity over time.

In some embodiments, the input device 100 is implemented with additionalinput components that are operated by the processing system 110 or bysome other processing system. These additional input components mayprovide redundant functionality for input in the sensing region 120, orsome other functionality. FIG. 1 shows buttons 130 near the sensingregion 120 that can be used to facilitate selection of items using theinput device 100. Other types of additional input components includesliders, balls, wheels, switches, and the like. Conversely, in someembodiments, the input device 100 may be implemented with no other inputcomponents.

In some embodiments, the input device 100 comprises a touch screeninterface, and the sensing region 120 overlaps at least part of anactive area of a display screen. For example, the input device 100 maycomprise substantially transparent sensor electrodes overlaying thedisplay screen and provide a touch screen interface for the associatedelectronic system. The display screen may be any type of dynamic displaycapable of displaying a visual interface to a user, and may include anytype of light emitting diode (LED), organic LED (OLED), cathode ray tube(CRT), liquid crystal display (LCD), plasma, electroluminescence (EL),or other display technology. The input device 100 and the display screenmay share physical elements. For example, some embodiments may utilizesome of the same electrical components for displaying and sensing. Asanother example, the display screen may be operated in part or in totalby the processing system 110.

It should be understood that while many embodiments of the invention aredescribed in the context of a fully functioning apparatus, themechanisms of the present invention are capable of being distributed asa program product (e.g., software) in a variety of forms. For example,the mechanisms of the present invention may be implemented anddistributed as a software program on information bearing media that arereadable by electronic processors (e.g., non-transitorycomputer-readable and/or recordable/writable information bearing mediareadable by the processing system 110). Additionally, the embodiments ofthe present invention apply equally regardless of the particular type ofmedium used to carry out the distribution. Examples of non-transitory,electronically readable media include various discs, memory sticks,memory cards, memory modules, and the like. Electronically readablemedia may be based on flash, optical, magnetic, holographic, or anyother storage technology.

The input device 100 may be based on ultrasound technology, and detectinput objects using the differences in the acoustic index of refractionof the materials in the paths of the ultrasound waves. The ultrasoundwaves reflect at the interfaces of different acoustic indices ofrefraction. The reflections indicate what was in the paths of thesewaves, and where they were located along the paths. Thus, ultrasoundsensor devices can obtain information from reflected ultrasound wavesabout locations and characteristics of materials encountered.

Compared to some other touch sensing technologies, ultrasound sensordevices may be made less susceptible to EMI, to ESD, to geometricdistortion, to edge effects, to contamination by dirt or oils, etc.Ultrasound sensor devices may also be made thin, and some embodimentsmay be just a few mm thick. Further, ultrasound sensor devices canrespond to input by objects regardless of the conductivity, the opticalreflectivity, or other aspects of the input objects, thus makingselection using the input device more convenient, versatile andefficient for the user.

FIG. 2 is a partial schematic of the exemplary input device 100illustrating an example of an ultrasound wave (i.e., a transmittersignal 200) penetrating a cover material 202 disposed over a sensormodule 204 of the input device 100 and interfacing with the input object140. The sensor module 204 is configured to make available the resultingsignal, which includes effects indicative of the input object 140relative to the sensing region 120, to the processing system 110. In theembodiment depicted in FIG. 2, the input object 140 is in contact withthe cover material 202. The ultrasound wave encounters two interfaces208, 210 where the different acoustic indices of refraction change.Thus, the ultrasound waves reflect at each of these interfaces 208, 210.These reflected ultrasound waves 212, 214 (“echoes”) carry informationabout the acoustic environment. Echoes are also further reflected asthey encounter other interfaces (not shown) with unmatched acousticindices of refraction, so the actual map of ultrasound waves is muchmore complicated than what is shown in FIG. 2. The sensor module 204receives the echoes that reach the sensor module 204, and uses theseechoes to determine information about what caused the reflections bymaking available the resulting signal to the processing system 110.

Any appropriate ultrasound transmitter technology may be used togenerate the ultrasound waves used by the input device 100. For example,ultrasound transmitters may use piezoelectric technology to provide anultrasound transmitter signal which may be driven onto the sensor module204. The ultrasound transmitters may also be of any appropriate shapeand cover any appropriate number of dimensions. For example, atransmitter may be in the form of a point transmitter, a lineartransmitter, a planar transmitter, or combinations of two or morethereof. Other example transmitter designs may incorporate curved linesor surfaces, multiple ultrasound transmitters, etc.

Similarly, any appropriate ultrasound detector technology may be used todetect the echoes. For example, ultrasound detectors may usepiezoelectric technology to generate a signal indicative of the inputobject 140 relative to the sensing region 120. The ultrasound detectorsmay also be of any appropriate shape and cover any appropriate number ofdimensions. For example, the detector may be in the form of a pointultrasound detector, a one-dimensional (1D) linear ultrasound detector,a two-dimensional (2D) ultrasound detector, or combinations of two ormore thereof. Other example ultrasound detector designs may incorporatecurved lines or surfaces, multiple detectors, etc.

Ultrasound detectors, such as but not limited to those described above,may be configured to detect near-field images, or far-field images withbeam steering to some part farther away from the sensor. For example, a2D detector may acquire a near-field C-mode image of ultrasoundreflectivity in a plane that is parallel to the plane of thetransducers. As another example, a linear detector may be used toacquire a B-mode image of ultrasound reflectivity in a plane thatcontains the line of detectors. As a further example, a planar detectormay be used to acquire a three-dimensional image of space near thedetector.

Further, the ultrasound transmitter and ultrasound detector may comprisecomponents configured to both transmit as well as receive, or componentsthat are dedicated for either transmission or reception. For example,some ultrasound transducers are well suited to transmit ultrasound aswell as receive ultrasound, and so can be used as ultrasoundtransmitters and as ultrasound detectors. This may be done in someembodiments using a time-multiplexed approach. As another example, sometransducers are better suited for transmission and some transducers arebetter suited for reception. Other considerations in whether or not touse combined or dedicated ultrasound transmitters and receivers includethe type of image to be obtained, the type of object to be imaged, thephysical geometry and arrangement of components of the system, etc.

FIG. 3 shows an example stack-up of one embodiment of a sensor module204 that may be used in the input device 100 to sense the input object140 (shown as a finger in FIG. 3) that is contacting an input surface302 in the sensing region 120. The input surface 302 is provided by aplaten 304 disposed between the input object 140 and a sensor element306 of the sensor module 204. The sensor element 306 may be configuredas the ultrasound transmitter, the detector, or a combined ultrasoundtransmitter and detector. If the acoustic index of the refraction of thetypical input object is known, the platen 304 may be configured to havea similar acoustic index of refraction in some embodiments. A backing308 is shown supporting both the platen 304 and the sensor element 306.

FIG. 4 is a partial cross sectional schematic view of one embodiment ofthe sensor element 306. The sensor module 204 generally includes aplurality of sensor elements 306, each of which operable to makeavailable a resulting signal to the processing system 110 of the inputdevice 100. The sensor element 306 generally includes a first electrode402 and a second electrode 404 sandwiching a piezoelectric material 406.

The piezoelectric material 406 in the sensor element 306 when used as apiezoelectric transducer deforms in response to an applied charge(positive or negative). In a piezoelectric ultrasound transmitterapplication, charge can be applied to deform the piezoelectric material406 to create ultrasound waves. Also, piezoelectric material 406 in thesensor element 306 when used as a piezoelectric detector will supply orsink charge in response to deformation. In an ultrasound detectorapplication, ultrasound waves impacting the sensor element 306 apply aforce, which deforms the piezoelectric material 406, thus generatingcharge. The instantaneous force applied by ultrasound waves is theinstantaneous sound pressure integrated over the relevant sensor area ofthe sensor element 306. This force is generally monotonic with respectto the sound pressure level of the incident waves multiplied by therelevant sensor area of the sensor element 306. This force usuallycreates a charge that is roughly proportional to the applied force, overthe operating range of the sensor element 306.

Piezoelectric transducers used in sensor elements 306 suitable forultrasound detection may generate a resulting charge transfer on theorder of 1-20 picoCoulombs per Newton of applied force. This chargetransfer may be measured directly, amplified, integrated on a capacitorof the processing system 110 to produce a voltage, etc. In oneembodiment, the instantaneous rate of charge transfer (Coulombs/second)is current. This current may be converted to a voltage (such as bypassing it through a resistor).

In those embodiments where the sensor element 306 is used as anultrasound detector, the first electrode 402 may be connected to areference node such as ground and a receiver circuit of the processingsystem 110 may be coupled to the second electrode 404 to receive theoutput of the sensor element 306 for analysis. In those embodimentswhere sensor module 204 is fabricated from an array of sensor elements306 configured as piezoelectric transducers, the processing system 110may include an array of corresponding receiver circuits coupled to thearray of sensor elements 306.

The sensor elements 306 configured as ultrasound detectors may bedesigned and sized based on the finest feature that the sensor module204 would be configured to detect. For example, sensor elements 306 withsensing surfaces of 50 μm×50 μm may be fine enough to distinguish ridgesand valleys of human fingerprints. Ultrasound detectors with largersensing surfaces, or sensing surfaces having different aspect ratios,may distinguish between larger objects. Where the sensing surfaces aresmall, the resulting charge per transducer due to ultrasound reflectionsduring normal operation may be too small to measure accurately withsimple circuits. Some embodiments accumulate charge over multiple cyclesto increase the size of the charge being measured.

As the leading edge of an ultrasound reflection compresses thepiezoelectric material 406 of the sensor element 306, a charge of thepolarity associated with compression results. Then, as the trailing edgeof an ultrasound pulse decompresses the piezoelectric material 406 ofthe sensor element 306, a charge associated with decompression (ofopposite polarity) results. Some embodiments of the processing system110 rectify these opposite-polarity charges to the same polarity asfurther discussed below.

FIG. 5 is a schematic diagram illustrating one example of an array 500of sensor elements 306 configured as piezoelectric detectors coupled toa detection module 502 of the processing system 110. Although theexemplary array 500 of FIG. 5 has three rows and three columns of sensorelements 306, the array 500 of sensor elements 306 may be arranged inalternative configurations having more or less sensor elements 306comprising the sensor module 204. The detection module 502 includesreceiver circuits 504, and in the embodiment illustrated in FIG. 5, eachreceiver circuit 504 is coupled to a respective one of the sensorelements 306 of the sensor module 204.

In one embodiment, the detection module 502 is fabricated using TFT(thin-film-transistor) technology on an appropriate substrate 514, suchas glass, plastic, or other suitable substrate, on which the sensorelements 306 are formed. In another embodiment, at least a portion ofthe detection module 502 is formed by an integrated circuit, i.e., achip, which may be mounted proximate the substrate 514 on which thesensor elements 306 are formed, for example on a flexible tail securedto the substrate 514. In another embodiment, at least a portion of thedetection module 502 may be physically integrated in other parts of theelectronic system utilizing the input device 100.

The processing system 110 may also include a row select module 506 and acolumn multiplexer module 508. The row select module 506 is a logiccircuit operable to select among the different rows of sensor elements306. The column multiplexer module 508 multiplexes the readout of thecolumns of sensor elements 306 to readout circuitry 512. The inclusionof the row select module 506 and the column multiplexer module 508 mayreduce the number of different readout circuits utilized in the inputdevice 100.

In the example illustrated in FIG. 5, a timing module 510 and/or atransmitter module 520 may be included as part of the processing system110. The timing module 510 generates timing signals that synchronizesthe different modules of the processing system 110. For example, a firstsignal generated by the timing module 510 may be provided to thetransmitter module 520. The transmitter module 520 may be configured todrive a transmitter signal onto the array 500 of sensor elements 306.The transmitter signal may be an ultrasound wave generated by anultrasound driver of the transmitter module 520. Although thetransmitter module 520 is shown as a separate component from the sensorelements 306 in FIG. 5, the transmitter module may share none, some, orall of the components of the sensor elements 306.

In another example, the timing module 510 may generate one or moretiming signals utilized by the detection module 502 to process theresulting signals received from the array 500. In the embodiment of FIG.5, the timing module 510 provides a first timing signal and a secondtiming signal to the detection module 502 which is utilized toselectively activate the detection module 502 to charge an integratingcapacitor of the detection module 502, as further discussed below withreference to FIG. 6. The timing module 510, transmitter module 520, maybe mounted to the substrate 514 or other portion of the input device100.

Continuing to refer to FIG. 5, in one embodiment, the exemplary array500 includes nine second electrodes 404 of each piezoelectric sensorelement 306 associated with each receiver circuit 504. Eachpiezoelectric sensor element 306 shares the same first electrode 402. Inother embodiments, array 500 includes various numbers of secondelectrodes 404, piezoelectric sensor elements 306 and receiver circuits504. Further, in various embodiments each or a portion of eachpiezoelectric elements 306 may share the same first electrode 402.

In some embodiments, the array 500 of sensors elements 306 comprisingthe sensor module 204 is part of a TFT panel. For example, the array 500of sensors elements 306 and/or the receiver circuits 504 may bemanufactured with TFT technology, the substrate 514 may be TFT glass,and the second electrode 404 may be a top layer of the TFT panel. Thetop electrode of the TFT panel may be placed in direct contact with thearray 500, or be the second electrode 404 of the array 500 ofpiezoelectric transducers being in contact with the piezoelectricmaterial 406. Alternatively, the TFT substrate containing an array ofthe detection module 502 may be connected to the array 500 of sensorelements 306 configured as piezoelectric transducers in a fashionsimilar to how a readout IC (ROIC) is attached to an image sensingarray.

FIG. 5 shows a specific example of the array 500 and detection module502, and other embodiments may differ. For example, some embodiments mayhave a different number of rows, a different number or columns, or adifferent number of total pixels (i.e., sensor elements 306). As anotherexample, some embodiments may not have a column multiplexer module 508.As a further example, some embodiments utilizing TFT technology may havedifferent components than shown in FIG. 5 residing on the same TFTpanel. As yet another example, some embodiments may contain amany-to-one or one-to-many ratio between receiver circuits 504 andsensor elements 306. That is, some embodiments may have a many-to-oneratio where one sensor element 306 is shared by multiple receivercircuits 504; and some embodiments may have a one-to-many ratio whereone receiver circuit 504 is shared by multiple sensor elements 306.

FIG. 6 illustrates one embodiment of the receiver circuit 504 of thedetection module 502 coupled to an output 606 of the sensor module 204.Although only one output 606 is shown connecting one of the sensorelements 306 comprising of the array 500 to a single receiver circuit504, it is understood that the array 500 includes a plurality of outputs606 each coupling a respective one of the sensor elements 306 of thearray 500 to a respective one of the receiver circuits 504 comprisingthe detection module 502. The detection module 502 may also include afirst switch 602 and a first integrating capacitor 604. As discussedabove, the sensor element 306 of the sensor module 204 is operable tomake resulting signals available to the receiver circuit 504, theresulting signals including positive and negative polarities, andincluding effects indicative of the input object 140 relative to thesensing region 120 adjacent the array 500 of the sensor module 204. Thereceiver circuit 504 is operable to receive the resulting signal fromthe sensor element 306 and charge the first integrating capacitor 604coupled to the receiver circuit 504 with a rectified signal in responseto receiving the resulting signal. The rectified signal generated by thereceiver circuit 504 may be fully rectified or half rectified. Stated inanother manner, rectified signal generated by the receiver circuit 504is of a single polarity regardless of the positive and negativepolarities of the received resulting signal. The receiver circuit 504may generate the rectified signal in response to only the positivepolarities of the received resulting signal, the negative polarities ofthe received resulting signal, or both the positive and negativepolarities of the received resulting signal. The receiver circuit 504may output the resulting signal as described above utilizing anysuitable configuration of circuit elements, for example, utilizing oneor more current mirrors.

In the embodiment depicted in FIG. 6, an output of the receiver circuit504 is coupled to the first switch 602 and to the first integratingcapacitor 604. The receiver circuit 504, the first switch 602 and thefirst integrating capacitor 604 may be embodied as an integratedcircuit. In the embodiment depicted in FIG. 6, the first switch 602 maybe in the form of a transistor, which may be activated by a signal fromthe row select module 506. When activated to open, the first switch 602couples the first integrating capacitor 604 to the readout circuitry512, thereby allowing the first integrating capacitor 604 to beaddressable by the processing system 110 so that information of theinput object 140 relative to the sensing region 120 may be determined.

The receiver circuit 504 is illustrated in the embodiment of FIG. 6 as atransistor network 600. The transistor network 600 is operable toreceive the resulting signal from the sensor element 306 and charge thefirst integrating capacitor 604 coupled to the receiver circuit 504 withthe rectified signal in response to receiving the resulting signal. Inone embodiment, the transistor network 600 includes a first transistornetwork 610, a second transistor network 620, and a third transistornetwork 630. The first transistor network 610 includes an input 611, afirst output 612 and a second output 613. The input 611 of the firsttransistor network 610 is coupled to a constant first voltage source 618that provides a constant voltage to the first transistor network 610.The first output 612 of the first transistor network 610 is coupled to afirst input 621 of the second transistor network 620 and a first input631 of the third transistor network 630. The second output 613 of thefirst transistor network 610 is coupled to a second input 622 of thesecond transistor network 620 and a second input 632 of the thirdtransistor network 630. In one embodiment, the first transistor network610 includes two transistors 614, 615 arranged as a current mirror, suchthat the transistors 614, 615 share the common input 611, while thetransistor 614 provides the first output 612 and the transistor 615provides the second output 613.

The second transistor network 620 and the first transistor network 610may be activated to charge the first integrating capacitor 604 inresponse to receiving the positive polarities of the resulting signalreceived from the sensor module 204. The gate of transistor 624 of thesecond transistor network 620 is coupled to an output 606 of one of thesensor elements 306 comprising the array 500. In one embodiment theoutput 606 of the sensor elements 306 is the second electrode 404. Anoutput 623 of the second transistor network 620 is coupled tosubstantially constant voltage value (i.e., system ground or some othersubstantially constant voltage value) 608 through a second switch 640.The second switch 640 may be in the form of a transistor, operable tocouple the output 623 of the second transistor network 620 to ground 608in response to receipt of the first timing signal provided by the timingmodule 510.

In the embodiment depicted in FIG. 6, the second transistor network 620includes a first transistor 624 and a second transistor 625. The firsttransistor 624 is operable to connect the first input 621 with theoutput 623 while the second transistor 625 is operable to connect thesecond input 622 with the output 623. A voltage signal is developedacross the resistor 644 in response to charge from the output 606 of thearray 500 flowing through the resistor 644. The current through thefirst transistor 624 changes in response to receipt of this resultingvoltage signal. The current through the second transistor 625 changes inthe opposite direction so that the sum of currents through transistors624 and 625 remains substantially constant.

The third transistor network 630 and the first transistor network 610may be activated to charge the first integrating capacitor 604 inresponse to receiving the negative polarities of the resulting signalreceived from the sensor module 204. The gate of transistor 635 of thethird transistor network 630 is coupled to the output 606 of one of thesensor elements 306 comprising the array 500. An output 633 of thesecond transistor network 630 is coupled to substantially constantvoltage value (i.e., system ground or some other substantially constantvoltage value) source 608 through a third switch 646. The third switch646 may be in the form of a transistor, operable to couple the output633 of the third transistor network 630 to substantially constantvoltage value source 608 in response to receipt of the second timingsignal provided by the timing module 510.

In the embodiment depicted in FIG. 6, the third transistor network 630includes a first transistor 634 and a second transistor 635. The firsttransistor 634 is operable to connect the first input 631 with theoutput 633 while the second transistor 635 is operable to connect thesecond input 632 with the output 633. A voltage signal is developedacross the resistor 644 in response to charge from the output 606 of thearray 500 flowing through the resistor 644. The current through thesecond transistor 635 changes in response to receipt by transistor 635of this resulting voltage signal. The current through the firsttransistor 634 changes in the opposite direction so that the sum ofcurrents through transistors 634 and 635 remains constant.

In one embodiment, the transistor network 600 described above providescharge to the first integrating capacitor 604 with a polarity responsiveto which switch 640, 646 is closed. Thus, by providing either of thefirst or second timing signals to control the open/closed state of theswitches 640, 646, the portions of the transistor network 600 may beselectively activated to integrate a charge onto the first integratingcapacitor 604, either during periods of the positive polarities of theresulting signal, during periods of the negative polarities of theresulting signal, or during periods of both positive and negativepolarities of the resulting signal.

In various embodiments, a second receiver circuit 504 is operative tocharge a second integrating capacitor 604 utilizing another transistornetwork 600 in a similar manner as described above. Respective groups ofassociated receiver circuits (such as receiver circuit 504), integratingcapacitors (such as integrating capacitor 604) and switches (such asswitch 602) are utilized for the other remaining sensor elements 306comprising the array 500 to handle the resulting signals from eachoutput 606 of the sensor elements 306.

In the embodiment depicted in FIG. 6, the transistor network 600comprises receiver circuit 504 and associated first switch 602 and firstintegrating capacitor 604, which may be matched one-to-one with eachsensor element 306 comprising the array 500 of piezoelectrictransducers. In various embodiments, transistor network 600 may be oneof an array of transistor networks. The arrays of transistor networks(one of which is shown in FIG. 6), may be fabricated using TFT processeson glass or another substrate. The receiver circuit 504 of FIG. 6 may beoperated to (a) synchronously rectify charge pulses from thepiezoelectric transducer (which varies in polarity with the leading andtrailing edge of the ultrasound pulse), (b) amplify the rectifiedpulses, (c) integrate and store the rectified and amplified chargepulses onto a storage capacitor, (d) allow range-gating, and (e) provideaddressable readout of the charge stored on a storage capacitor.

In the embodiment depicted in FIG. 6, an ultrasound wave front, forexample, a transmitter signal driven onto the sensor module 204,impinges on the piezoelectric material 406 of the sensor element 306.The common electrode serves as the first electrode 402 for all of thesensor elements 306 in the array 500, and is grounded in this example.One second electrode 404 of the many second electrodes 404 comprisingthe array 500 is shown in FIG. 6, while the other second electrodes 404are not shown for the sake of clarity, but it is to be understood thatthe non-shown second electrodes 404 are each coupled to a respective andseparate receiver circuit 504 comprising the detection module 502. Theshading of the wave front indicates that the front has differentmagnitudes at different portions of the common first electrode 402, andaffects different portions of the piezoelectric material 406differently. The part of the waveform affecting the piezoelectricmaterial 406 associated with the second electrode 404 shown causescharge to flow through the resistor 644, generating a voltage waveformshown as waveform 650. In one embodiment, the voltage waveform 650 isthe resulting signal at the gate of the transistor 624 in the receivercircuit 504.

The receiver circuit 504 shown in FIG. 6 may be operated as follows. Thetiming module 510 generates the first signal that defines when theultrasound transmitter module 520 emits ultrasound waves that are drivenonto the array 500. The timing of the ultrasound waves may be based onthe finest feature to be imaged. For example, various embodiments of thetiming module 510 may produce waves at 1 MHz-1 GHz, where higherfrequencies are more conducive to detection of smaller features of theinput object 140 within the sensing region 120.

The timing module 510 also generates the first and second signals thatcorrelate with the rising edges and the falling edges (i.e., thepositive and negative polarities) of the ultrasound pulses (i.e., thetransmitter signal) impinging on the piezoelectric material 406, whichin turn generate the resulting signal with correlating positive andnegative polarities. The widths and positions of these highs of thefirst and second signals may be determined for synchronousrectification, range-gating, and/or some other consideration.Range-gating, to control the depth of the plane to be imaged, may beaccomplished by adjusting the timing of the first and second signalsrelative to the pulse timing applied to the ultrasound transmittermodule 520 by the timing module 510.

Thus, the first signal is high during the time period at which theleading edge of each ultrasound pulse of the transmitter signalpropagates through the sensor element 306, and this turns on the secondswitch 640 during the leading edge of each ultrasound wave. When thesecond switch 640 is activated, current is allowed to flow throughtransistors 624, 625, 614 and 615. Meanwhile, the second timing signalis low, keeping transistors 646, 634 and 635 off. This results in chargebeing integrated onto the integrating capacitor during only positiveportions of the resulting signal.

The current flowing through transistor 624 is (I+i(t)). I is a quiescentcurrent that results from the voltage provided by the second voltagesource 642, and i(t) is a current of a first polarity (e.g., positivecurrent) due to the voltage developed across the resistor 644 as chargeof a first polarity (e.g., positive charge) is generated by thepiezoelectric material 406.

The current mirror formed by the first transistor network 610 mirrorsthe current flowing through the transistor 624 (I+i(t)) through thetransistor 615. The same quiescent current, I, flows through transistor625 due to the voltage provided by the second voltage source 642. Thus,a net current of i(t) flows into the first integrating capacitor 604.

Analogously, when the second timing signal provided by the timing module510 is high and first timing signal is low during the falling edge(i.e., the negative polarities) of each ultrasound pulse of thetransmitter signal, a charge of a second polarity opposite to the firstpolarity (e.g., negative charge) is generated by the piezoelectricmaterial 406. However, with rectification, the current flow into thefirst integrating capacitor 604 is still current of the first polarity(e.g., a positive current) i(t).

After N number ultrasound transmitter signal pulses, the charge on thefirst integrating capacitor 604 is increased by the amount ΔQ, whereΔQ=2N×|Δq|×ROLOAD*gm*K. In this equation, ΔQ=charge increase on thefirst integrating capacitor 604, N=number of pulses in the transmittersignal, Δq=charge generated by the piezoelectric material 406 at eachedge of an ultrasound pulse of the transmitter signal, ROLOAD=loadresistance in the receiver circuit 504, gm=small-signal transconductanceof transistors 624, 625, 634 and 635 and K=current ratio of the currentmirror provided by the first transistor network 610. Some embodimentsmay use K=1 for improved matching.

After M ultrasound transmitter signal pulses have been received, thefirst switch 602 is turned on by a row select signal provided by the rowselect module 506. M may be a predefined number of transmitter signalpulses. When the first switch 602 is on, the first integrating capacitor604 is connected through the first switch 602 to the external readoutcircuitry 512. The readout circuitry 512 can read the voltage on thefirst integrating capacitor 604 and then determine the accumulatedcharge based on this voltage, or directly read the charge accumulated onintegrating capacitor 604. After readout is complete, the readoutcircuitry 512 can reset the first integrating capacitor 604 prior toopening the first switch 602 and readying the receiver circuit 504 foranother iteration of detecting presence of the input object relative tothe sensing region 120.

Some embodiments read the voltage on integrating capacitor 604. Otherembodiments read the accumulated charge rather than the voltage onintegrating capacitor 604. The other embodiments may be designed suchthat: (1) voltage-dependent nonlinearities of the value of integratingcapacitor 604 do not substantially affect the amount of stored charge,(2) process and temperature variations of the value of integratingcapacitor 604 do not affect the amount of stored charge, (3) parasiticcapacitance on the pixel column node (i.e., sensor element 306) does notaffect the amount of stored charge, or for some other reason.

Also, many alternatives and variations of the circuit of FIG. 6 arepossible. For example, cascode transistors may be added in series witheach of the transistors comprising the second and third switches 640,646 (between the second switch 640 and the node common to transistors624, 625, and between the third switch 646 and the node common totransistors 634, 635). This configuration may increase the linearoperating range of the receiver circuit 504. As another example, a supercurrent mirror, such as a Wilson-super current mirror, may be used inplace of the mirror provided by the first transistor network 610. Thisconfiguration of the receiver circuit 504 can increase the accuracyand/or the linear operating range of the circuit.

As yet another example, the receiver circuit 504 may be built on someother type of substrate or using some other processes. As a specificexample, the circuitry may be built on a semiconductor substrate (suchas a silicon wafer) using semiconductor processing technology. In someembodiments, the second electrodes 404 are connected to the relevantpixel columns by row-select transistors disposed on a TFT. In otherembodiments, the receiver circuits 504 are not on the TFT, but are partsof integrated circuits such as ASICs which may reside on a flexible tailcoupled to the substrate 514, or in another part of the processingsystem 110 or electronic system utilizing the input device 100. Thepixel columns are communicatively coupled to the ASIC, and thusselectively coupled to the relevant receiver circuits 504. Operation canbe analogous to what is discussed above. Such embodiments may providefor higher performance or speed in some cases.

It is contemplated that at least one or more of the receiver circuits504, the timing module 510 and the readout circuitry 512 comprising thedetection module 502 may be embodied in an integrated circuit, such asASICs. For example, the receiver circuits 504, the timing module 510 andthe readout circuitry 512 may be embodied in a single integratedcircuit. In another example, the receiver circuits 504, the timingmodule 510 and the readout circuitry 512 may be embodied in two or moreseparate and communicating integrated circuits. The receiver circuits504 residing in the integrated circuit are coupled to the array 500 ofthe sensor module 204 as described above, while the readout circuitry512 makes information obtained from the array 500 available for use bythe electronic system incorporating the input device 100. The proximityof the integrated circuit to the array 500 reduces the combination timebetween the circuits and sensors, thereby allowing faster read times andsampling. The proximity of the integrated circuit(s) to the array 500also reduces potential damage due to electrostatic discharge (ESD) andadditionally improves the accuracy of signal transmission throughreduced susceptibility to electromagnetic interference (EMI).

Also, the receiver circuits 504 described herein are generallyapplicable for use with sensor elements 306 configured as piezoelectricultrasound detectors. For example, it is applicable to a wide variety ofshapes and arrangements of piezoelectric detectors, and it is applicableregardless of the location of the input object 140 to be imaged and theultrasound transmitter of the ultrasound wave, as long as the reflectedwave reaches the detectors. As another example, the described receivercircuit 504 may be used in a phased array of receivers to accomplishbeam steering for A-mode or B-mode ultrasound imaging. The phasing maybe accomplished by adjusting the timing of the first and second timingsignals on a per-pixel basis.

FIG. 7 is a flow diagram of one embodiment of a method 700 for sensingan input object relative to a sensing region of an ultrasound sensordevice that may be practiced using at least a portion of the inputdevice 100 or other suitable input device. The method 700 begins at step702 by receiving a first resulting signal. As discussed above, the firstresulting signal includes positive and negative polarities, and alsoincludes effects indicative of the input object 140 relative to thesensing region 120. At step 704, the first integrating capacitor 604 ischarged with a first rectified signal in response to receiving the firstresulting signal.

The method 700 may further include the step of driving the transmittersignal onto a plurality of pixel electrodes of a piezoelectrictransducer array, a first pixel electrode of the plurality of pixelelectrodes providing the first resulting signal, wherein the pixelelectrodes are the parts of the sensor elements 306 of the array 500.

The method 700 may also further include the step of generating the firstrectified signal in response to a timing signal synchronized with thetransmitter signal.

The method 700 may also further include the step of receiving a secondresulting signal comprising positive and negative polarities, the secondresulting signal comprising effects indicative of the input objectrelative to the sensing region, wherein the second resulting signal isreceived from a second pixel electrode of the plurality of pixelelectrodes. The method 700 may also further include the step of charginga second integrating capacitor with a second rectified signal inresponse to receiving the second resulting signal.

The method 700 may also further include the step of integrating chargeonto the integrating capacitor in response to at least one of thepositive and the negative polarities of the first resulting signal.

Thus, subsystem, system and method for sensing an input object relativeto a sensing region of an ultrasound sensor device have been described.The invention described herein is less susceptible to damage and/orinaccurate output due to electrostatic interference (EMI) andelectromagnetic discharge (ESD) as compared to conventional capacitivesensing devices. Moreover, the ultrasonic sensing system describedherein enables the detection of both conductive and non-conductiveobjects relative to the sensing region, thus allowing a wide variety ofinputs device types to be utilized. Furthermore, the ultrasonic sensingsystem described herein less susceptible to inaccuracies due to theeffects of dirt, oils and other contaminants as compared to conventionaloptical sensing devices, thereby providing a more robust input device.

What is claimed is:
 1. A subsystem for sensing an input object relativeto a sensing region of a sensor device, the subsystem comprising: afirst circuit comprising: an input for receiving a first resultingsignal, wherein the first resulting signal is in a form of a waveformcomprising positive and negative polarities, the first resulting signalcomprising effects indicative of the input object relative to thesensing region; a first transistor network; a second transistor network;and an output; a first switch coupled to the output of the firstcircuit; and a first integrating capacitor coupled to the output of thefirst circuit, to a substantially constant voltage source and to thefirst switch, wherein the second transistor network and the firsttransistor network provide a first portion of a first rectified signalto the first integrating capacitor based on the positive polarities ofthe resulting signal.
 2. The subsystem of claim 1, wherein the sensingregion of the sensor device comprises an ultrasound sensor device. 3.The subsystem of claim 1, wherein the sensor device is configured as afingerprint sensing device.
 4. The subsystem of claim 1, wherein thefirst circuit further comprises: a third transistor network operablewith the first transistor network to provide a second portion of thefirst rectified signal to the first integrating capacitor based on thenegative polarities, the first portion of the first rectified signal andthe second portion of the first rectified signal having the samepolarity.
 5. The subsystem of claim 4, wherein the first circuit isoperable to: turn on the second transistor network in response to afirst timing signal; and turn on the third transistor network inresponse to a second timing signal.
 6. The subsystem of claim 1 furthercomprising: a second circuit having an input for receiving a secondresulting signal comprising positive and negative polarities, the secondresulting signal comprising effects indicative of the input objectrelative to the sensing region; and a second integrating capacitorcoupled to the output of the second circuit, wherein the circuit isoperable to output a rectified signal to the second integratingcapacitor.
 7. The subsystem of claim 1, wherein the first transistornetwork and the second transistor network are disposed on a thin-filmtransistor substrate.
 8. A system for sensing an input object relativeto a sensing region of a sensor device, the system comprising: a firstsubstrate; an array of sensor electrodes disposed on the first substrateand operable to provide a first resulting signal, wherein the firstresulting signal is in a form of a waveform comprising positive andnegative polarities in response to presence of the input object in thesensing region; and a detection module comprising a first input coupledto the array of sensor electrodes, an output, and a plurality oftransistor networks, wherein the plurality of transistor networksprovide a first rectified signal to a first integrating capacitor of thedetection module, wherein the first rectified signal is based on thefirst resulting signal.
 9. The system of claim 8 further comprising: asecond substrate, wherein the second substrate is a thin-film transistorsubstrate; and wherein at least a portion of the detection module isdisposed on the second substrate.
 10. The system of claim 8, wherein thefirst substrate is a thin-film transistor substrate.
 11. The system ofclaim 8 further comprising: a transmitter module configured to drive thetransmitter signal onto the array of sensor electrodes.
 12. The systemof claim 8, wherein providing the first rectified signal to the firstintegrating capacitor comprises: providing a first portion of therectified signal based on positive polarities of the first resultingsignal; and providing a second portion of the rectified signal based onnegative polarities of the first resulting signal.
 13. The system ofclaim 8, wherein the sensor device is an ultra-sound sensor device. 14.The system of claim 8, wherein the sensor device is configured to sensefingerprints.
 15. The system of claim 8, wherein the detection modulefurther comprises: a second input configured to receive a secondresulting signal from the array of sensor electrodes, wherein theplurality of transistor networks provide a second rectified to a secondintegrating capacitor of the detection module, wherein the secondrectified is based on the second resulting signal.
 16. A method forsensing features of an input object relative to a sensing region of asensor device, the method comprising: receiving a first resultingsignal, wherein the first resulting signal is in a form of a waveformcomprising positive and negative polarities, the first resulting signalcomprising effects indicative of the input object relative to thesensing region; and charging an integrating capacitor with a firstrectified signal with at least one of a plurality of transistornetworks, wherein the first rectified signal is based on the firstresulting signal.
 17. The method of claim 16 further comprising: drivinga transmitter signal onto a plurality of pixel electrodes.
 18. Themethod of claim 16, wherein generating the first rectified signal via aplurality of transistor networks comprises generating a first portion ofthe rectified signal based on the positive polarities and a secondportion of the rectified signal based on the negative polarities. 19.The method of claim 16 further comprising: receiving a second resultingsignal comprising positive and negative polarities, the second resultingsignal comprising effects indicative of the input object relative to thesensing region, wherein the second resulting signal is received from asecond pixel electrode of the plurality of pixel electrodes; andcharging a second integrating capacitor with a second rectified signalwith at least one of the plurality of transistor networks, wherein thesecond rectified signal is based on the second resulting signal.
 20. Themethod of claim 16, wherein the first resulting signal contains effectsindicative of ridges and valleys of a fingerprint.